Cisco Security Advisory – A vulnerability exists in the Session Initiation Protocol (SIP) implementation in Cisco IOS Software that could allow an unauthenticated attacker to cause a denial of service (DoS) condition on an affected device when the Cisco Unified Border Element feature is enabled.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/81598/cisco-sa-20090923-sip.txt
Source: https://packetstormsecurity.com/files/81598/Cisco-Security-Advisory-20090923-sip.html